Various products are used as coating agent aqueous dispersions for use in surface-treating agents for rubber-made sealing materials. For example, Patent Document 1 discloses a PTFE (polytetrafluoroethylene resin) aqueous dispersion composition comprising PTFE particles and a polyoxyalkylene alkyl ether-based compound, and optionally containing a film formation improver, such as an acrylic resin, a surfactant, or the like. Patent Document 1 indicates that this composition has a significantly high crack threshold thickness, and that a thickened film can be obtained even by one impregnation or coating of the composition. A flexibility evaluation, an adhesion evaluation, etc., among later-described various tests are satisfactory; however, an adhesion reduction evaluation by a humidification test is not satisfactory.
Patent Document 2 discloses a coating composition comprising perfluorocarbon polymer fine particles, mica or metal flakes, (meth)acrylic-based polymer, and a liquid carrier. This composition is mainly used for PTFE-coated cookware. Among later-described various tests, an adhesion evaluation is satisfactory; however, a flexibility evaluation and an adhesion reduction evaluation by a humidification test are not satisfactory.
Patent Document 3 discloses an aqueous coating agent composition comprising an ethylene-vinyl acetate copolymer resin emulsion and two or more types of PTFE resin powders having different particle diameters. Patent Document 3 indicates that this composition has excellent coating film adhesion, workability, heat resistance, and chemical resistance. Among later-described various tests, a flexibility evaluation and an adhesion reduction evaluation by a humidification test are satisfactory; however, an adhesion evaluation is not satisfactory.
Patent Document 4 discloses a non-stick coating containing fluoropolymer, acrylic polymer, and polyol or diol. Further, Patent Document 5 discloses an aqueous dispersion composition for coating fluororesin comprising a fluororesin particle dispersion and a depolymerizable acrylic resin particle emulsion.
However, because these compositions are sintered at 300° C. or higher, rubber deterioration occurs in fluororubber and silicone rubber, and rubber materials with low heat resistance, such as NBR, are significantly deteriorated. Accordingly, these compositions cannot be applied to seal parts.